Screw jack with a reversible motor and safety ejection means



July 19, 1949. R. LARAQUE SCREW 'JACK WITH A REVERSIBLE MOTOR AND SAFETYEJECTION MEANS Filed Jan. 5, 1948 4 Sheets-Sheet l July 19, 1949.LARAQUE 7 2,476,376

SCREW JACK WITH A REVERSIBLE MOTOR AND SAFETY EJECTIONMEANS Filed Jan.5, 1948 4 Sheets-Sheet 2 July 19, 1949. R. LARAQUE 2,476,376

scREw JACK WITH A REVERSIBLE MOTOR AND SAFETY EJECTION MEANS Filed Jan.5,1948 4 Sheets-Sheet 5 r LO R. LARAQUE SCREW JACK WITH A REVERSIBL July19, 1949.

E MOTOR AND SAFETY EJECTION MEANS Filed Jan. 5, 1948 4 Sheets-Sheet 4Patented July 19, 1949 SCREW JACK WITH A REVERS'IBLEMOTOR ANDSAFETYEJEGTION MEAN S1 Roland Laraque, Paris, France, assignor to SocieteAn'onyrne LAuxiliaire Industrielle', Paris,

France, a corporation of France Application January 5, 1948, Serial No.63.6 In France August; 9., 1.947

8 Claims.

The present invention has for its object to provide the new article ofmanufacture formed by a screw jack controlled by a reversible motor andprovided with a safety device acting in a given direction of actuation(ejection of the jack-rod), said device being adapted.- to be actuatedthrough a simple and fast actuating operation, in the event ofnon-operation or a check in the operation occurring for any reason andat any point of the stroke in said direction, of the motor whichnormally provides for such operation (such as an electric motor) A jackof the above character is applicable, by way of example and notoflimitation, in connection with the retracting operation of anaircraft-undercarriage or landing gear which is normally effected, bothfor retracting and projecting the undercarriage, through the rotation ofa reversible motor, and for which it is desired to avert theconsequences arising from an impossibility of projecting theundercarriage in a normal manner at a desired time.

To actuate said safety device, it is simply necessary to release, underthe action of a very slight actuating stress, a detent percussion memer,having a spring normally retained under tension, andthe release of whichis operative to open the check valve of a tank containing a pressurefluid. This fluid, through a conduct, 11-. necting it with the jack,

then penetrates into the safety device, first uncouples the rigidconnection between the control screw and the drive system connected withthe motor, then directly acts upon the screw-and-nut assembly of thejack causing this assembly to move in the manner of a piston within itscylinder and causing ac.- cordingly an ejection of the rod :and also, inthe exemplary application mentioned above, the ejection of theundercarriage rigidly coupled with the end of said assembly.

Further characteristics and features of the in! vention wil1 appear fromthe ensuing disclosure relating to a preferred embodiment of the reversible motor and safety ejection jack, illustrated by way ofindication and not of limitation in the accompanying drawing wherein:

Fig. 1 is a fragmentary longitudinal cross-section showing the driveportion and the safety ejection device for the rod. of the jack formingthe subject of this invention.

Fig. 2 shows in fragmentary longitudinal cross-section the portion ofthe jack to which attached the retractable undercarriage.

F 3 is a fragmentary longitudinal cross-seetion on. line III-III 015Fig. 2,

g. 4 is a cross-section showing the position occupied by certainelements of the jack; after admission of the pressure fluid into thesafety device.

Fig. 5v shows the position occupied by said elements after thescreW-and-nut assembly has been released from rigid connection with theengine controlled drive device.

Fig. 6 diagrammatically illustrates the jack in ejected position whenthe normal control device is being used.

Fig. '7 is a' diagram illustrating the jack in ejected position whenthesafety device is being used.

In Fig. 1 there has been illustrated the means used to drive the jack inits normal operation. In this case, the drive is transmitted from areversible motor I through a couple-limiting clutch means 2(diagrammatically indicated in the drawing) to a speed reducing gearingcontrolled as, follows: the drive portion of the clutch 2 is rigid withthe shaft 3 journalled in appropriate anti-friction bearings 4 mountedin the casing 5.. Said shaft has secured thereon a pinion 6 meshing withthe larger diameter portion of a gear I provided with two sets of teeth,said gear being fitted with appropriate anti-friction bearings 8supported on the fixed shaft 9 rigid with the casing 5. The smallerdiameter portion of the dual-toothed gear 1 meshes with a toothed gearl0 secured on a bushing H which rotates in appropriate anti-frictionbearings 12 and I3 supported in the casing 5.

The bushing l I terminates in a cylindrical portion i l of enlargeddiameter, the end face of which is adapted to engage through aclaw-clutch means l5, the head iii of the jack-screw I! which issupported at one of its ends by its nut l8, and at the opposite end in asuitable bearing l9 (see Fig. 2).

In order to prevent the head I6 of the jack screw H from becominguncoupled from the cylindrical portion 14 of the bushing H, said eyelindrical portion is formed with one or more recesses 20 the bottom orend-wall of which is formed by the periphery of a hollow piston 21axially slidable within the cylindrical portion l4 of the bushing II butmaintained in normal operative position of the device by means of abias-.- ing spring 22; said spring engages at one end the end wall ofthe hollow piston 21 and at its other end the end wall of thecylindrical portion IA of the bushing I I.

In each of said recesses 20 is arranged a ball 3 en a ing said recess soas to be more than 3 half embedded therein and which rests against theperipheral surface of the hollow piston 2i (Fig. 1). The ball isretained in its recess (irrespective of the attitude of the aircraft inflight) by means of a retaining socket 24. The other portion of the ball23 engages the bottom of an annular groove 25 of trapezoidalcross-section formed in the head I 6 of the screw I I. Theabove-described ball-and-groove locking device acts to prevent anylateral displacement of of the screw I! together with the interiorlythreaded member 58 which controls the helical movement of the screw IIthrough the'agency of the clutch claws I5, the head It of the screw I1with the end face of the cylindrical portion [4 of the bushing II.

The nut I8 is blocked against rotation through a telescopic tube 26 withwhich it is rigidly connected, said tube in turn being made rigid withthe tubular extension 21 (see Figs. 2 and 3) of a fork member 28 througha pin 29 on'which is mounted a key 30 for sliding displacement in a slot3i formed in said tubular extension 27. The fork 28 carries a pin 32 (ascrew-threaded end of which is provided with a nut 83) which makes ispossible to immobilize the pin 34 to which is attached the retractableundercarriage, not shown. The just described assembly thus provides auniversal or Cardan joint. On the other hand the casing 5 is extended onthe side of the telescopic tube 26 by a guiding tube 35 terminating in abearing or journal housing 36. The casing 5 is at its opposite endpivoted through a universal joint to the body of the aircraft throughthe use of a pivotal fork 31.

In normal operation of the screw jack forming the subject of thisinvention, the reversible rho-- tor l transmits its drive through areducing gearing and through the bushing III4 to the screw H which thenshifts its nut I8 along the tube 25. Said nut in its displacementcarries With it in either one or the other direction the telescopic tube26 with which it is rigid. The relative movement between the telescopictube 26 and the slotted fork element 21 gives rise at the start of eachstroke in either direction, to an initial lost motion phase for the tube26 and the pin 29 rigid therewith, prior to exerting any action upon theundercarriage itself. This lost motion serves to control the levers (notshown herein) which cause the unlatching of the undercarriage when inprojected position or the release of the undercarriage when in retractedcondition.

After the key 30 has engaged either one of the end walls of the slot 3I,the telescopic tube 26 causes the retractible undercarriage attached tothe jack shaft 34 (see Fig. 6), respectively to be raised when moving inone direction and to be lowered when moving in the opposite direction.In the accompanying drawing the raisin of the undercarriage is shown tobe effected upon contraction of the jack and the lowering of theundercarriage upon expansion of the jack.

Within the jack driving device which has just been described isaccommodated the safety lowering device. As may be ascertained from Fig.1 this device is of highly simple construction and operation and offersa minimum overall size or bulk, since it occupies the central portion ofthe jack according to the invention. Said safety lowering device iscontrolled by the hollow piston 2| mentioned above and on the face ofwhich initially acts the pressure medium. Said hollow piston carries apush rod 39 which at its opposite end extends through an extension 40 ofthe factelescopic tube, the fork member ing 5, slightly projectingoutwardly thereof. The push-rod 39 is separated from the extension 43 ofthe casing 5 by an annular duct or channel 4 I. A cap 42 threadedlyengaging the extension 40 of the casing 5 protects from any extraneousaction the end of the push-rod 39 (projecting out of the casing 5) andseals the end of the annular duct 4|. A certain amount of clearance isprovided between the central portion of the push-rod 39 and the internalportion of the bush H, so as thereby to define a sort of annular channel43. There is similarly provided at 44 a certain spacing between the endface of the bush II and the casing 5, for purposes to be describedlater. The hollow piston 2| is peripherally formed with an annulargroove 45 of trapezoidal cross-section.

There is formed in the casing 5 a screw-threaded aperture 46 adapted toreceive for instance the threaded connection of the flexible pipecommunicating with the above-mentioned pressure fluid tank.

Rotary joints 4! and 48 mounted on the bushing I I and the cylindricalportion I4 as well as the slidable joint 49 provided on the nut I8ensure fluid-tightness of the device.

Finally, the chamber of variable volume clefined by the tube 26 and thenut I8, the tube 35 and the bearing 36, serves as a pneumatic damper forthe safety ejection of the tube, through the provision of the tightseals 49 (on the nut I3) and 52 (on the bearing 26), as well as the ventoutlets 53 formed in the bearing 36 and which if desired may be providedadjustable through screws or loaded by an adjustable spring-biassedcheckvalve, not shown herein.

Should for any reason and at any point of its downward (jack expanding)stroke, the motor I break down, or should for any accidental cause suchas an abnormally tough area, the reaction be greater than the maximumpermissible sliding value for the stress-limiting clutch 2, the pilotwould then release the percussion member of the safety tank. Thepressure medium flows into the safety device, the result of this beingto displace the hollow piston 2| until it engages the end face of thecylindrical portion I4 (Fig. 4) while compressing its spring 22,blocking it by pressure action in its new position and uncovering theport 50 formed in the cylindrical portion I4 of enlarged diameter in thebushing II, and through which the pressure fluid penetrates into theexpansion chamber 5!. Under the effect of the pressure exerted by thenut I 8, the balls 23 are projected into the annular groove 45 andrelease the head I6 of the screw I1, which is thus disconnected from thecylindrical portion I4 of the bush II. The fluid pressure continuing tofurther act upon the surface of the nut I8, pushes the nut I8 and thescrew I1 through the tube 35, after the manner of a piston in itscylinder (see Figs. 5 and '7). The nut and its screw in turn carry withthem in their displacement, through the agency of the 28 (see Figs. 2and 3) with which the retractible undercarriage (not shown) is rigid,thus enabling the latter to be lowered.

After landing has been effected, in order to recondition or recock thesafety device of the jack according to the invention, the percussionmember of the safety tank is first cocked, the effect of this being toallow the check valve of the tank to drop back upon its seating and tovent the jack to atmosphere. Then the undercarriage and the jack aredisconnected. For

camera this purpose it is necessary to extract the pin 32 from:- thefork: 28hy loosening theanllt 33 (see Figs. 2 and: 3): therrvthe capi42i's .un-.: screwed (Fig. 1-)-. Since pressure :iszreli'eved from theface. of the hollow piston 2t" the latter will have been restored toits. initial position (as shown in Fig. I) by the action of the biasingspring 22. Thetelescopid tube 26 is then reinserted into the tube 35after having pressed the push-rod- 39; in the first pl-aceso astouncover the port fifi and thuszto -al-low' escape ofthefluid from tube35; and in the'second placeto allow the balls: 23.-. to be retracted soas to enable the head- It of the screw Hi to return to'its' place; Afterthe annular groove 25 0f the head 16* comes i ntoregister with therecesses 2-0 for the balls 23; the application of pressure isdiscontinued on the push-rod 39-; the'balls 2'3-then rideup alongthecam-surf ace of the annular "groove 45, and, while thusretnrni-ngtotheir place, they'latchingl'yconnect the head [B -ofthescrew H'- with the engine controlled driving device. The safetydeviceis then: cocked and in a condition toresume its iii-notion;

It will of course be understood that the exernplary embodiment describedabove and illustrated in the accompanying drawings is given merely byway of indication and not of limitation, and it maybe possibleto provideany modiflcations in the jack with a safetyrod-ejecting device accordingto theinvention, and to replace therein certain elements" by equivalentones without departing from thespirit' of the invention.

Thus for} example the jack according to the invention couldbe applied tothe control of a device other thanv a retractable aircraftundercarriage.

': What: is: claimed is:

l. A screw-jack device comprising'in combination a casinghavingan-elongated tubular portion, a tube telescopabl'e within said tubularportion in coaxial spaced relationtherewith slidable in the outerend'of' saidtubular portion; a structure to be-operatedby saiddevice-attached to the outerendof said'tube, a-nut member at the innerend of said tubenon-rotatably sealingly slidable in saidtubu-larportion,a screw-rod engaging said nut and extending in coaxial relation withboth said tubular portion and said tube, said screwrod when rotatedcausing said nut-and-tube assembly to move axially between a retractedand a projected position with respect to said casing, a reversiblepower-means outside said tubular casing, a drive connection extendingfrom said power-means'to a drive member in said casing opposite theinner end of said screw-rod, co-operating clutch means in said drivemember and in said inner end of said rod adapted to drivingly couplesaid rod and said member in rotation when said rod is in said retractedcondition, means to latch and unlatch said member and said inner end ofsaid rod with respect to each other when so coupled, pressure-fluidactuated means in said tubular casing, means to admit pressure fluidfrom an external source to one side of said lastmentioned means, saidmeans being operative, when so actuated, to first unlatch saiddrive-coupling between said rod and said member and then to cause saidfluid pressure to act upon said nut to impart a bodily axialdisplacement to said nutand-tube assembly together with said screw-rodfrom said retracted to said projected position thereof, therebyoperating said structure accordingly.

2. A screw-jack device as claimed in claim 1 6 wherein said latching:means comprises in combination: a head at thei-inner end-Jr of saidscrew; a pair of complementary generally interesting cylindricalsurfaces in: said; drive member and said head. respectively;circumferentially spaced recesses in the outer one of? said surfacesandcorrespondingly disposed-L apertures through the inner one of. saidsurfaces, and alatching ball adapted tobe. housed partly in each: one ofsaid recesses and partly in -the-related aperture, said pressureactuated means'being' operative, when unactuated, to retain: said ballsin such position and when actuated, to allow said balls-to drop throughsaid apertures completely out of the related recesses;

3. A screw-jack device as claimed in claim I wherein said drive-memberhas a cavity with cylindrical walls directed towards said screwrod, saidscrew-rod has a cavity with cylindrical walls directed towardssaidmember adapted to surround said first-mentioned cylindrical walls;annularly arranged clutch teeth at the endof said walls of said memberand complementary clutch-teeth in the-bottom'of said cavity in saidhead-, adapted to c'o-operate in rotational driving engagement witheachother when saidscrewrod is in said normal retracted position,circumferentially-spaced recesses in theinner peripheral surface ofsaid' cylindricalwall's of said screw-head and correspondingly-arrangedapertures throughsaid cylindrical walls of said member, a latching balladapted to be seated partly in each of said recesses and partly in therelated aperture in saidnormal retracted position of said screw-rod;-apiston sea-lingly slid able in said cavity of said member between aretracted latching position and a projected unlatching position withrespect thereto, and having a peripheral-annular groovearranged'to'regrister with said annular apertures only for saidprojected position of said piston to then allow said balls to drop intosaid groove, spring-means urging said piston to said retracted positionthereof, and said pressure-fluid when admitted urging said pistontowards said projected unlatching position thereof.

4; Ina-screw-jack'device as claimed in claim 1 wherein the innersurfa'ceof said' nut defines a fluid-tight enclosure with said casing, a hollowcylindrical portion on said member and a hollow cylindrical portion onthe inner end of said screw-rod surrounding said first-mentionedportion, complementary pairs of annularly arranged recesses in thecylindrical walls of said portions respectively and a set of balls eachmovable between a latching position wherein said ball partly engageseach one of said complementary pair of recesses in said cylindricalwalls respectively and an unlatching position wherein said ball isretracted out of the recess in said cylindrical wall of said screw-rodcavity, a piston formed with a peripheral groove sealingly slidable insaid member cavity, spring means urging said piston to a positionwherein said periphery thereof retains said balls in said latchingposition thereof, means to admit said pressure fluid into the chamberdefined between the inner walls of said member cavity and the adjacentside of said piston to thereby urge said piston to an unlatchingposition wherein said groove therein allows said balls to drop to saidretracted condition thereof, a port through the cylindrical wall of saidmember cavity arranged to be uncovered by said piston when urged to saidunlatching position, said port providing communication from said chamberto said enclosure to thereby cause said pressure-fluid to firstpositively force said balls to said retracted position thereof, and thento drive said nut together with said screw and said tube to saidprojected position thereof out of said tubular casing.

5. A screw-jack device as in claim 1 wherein said power-means comprisesa reversible electric motor secured outside of said tubular casing andsaid drive connection includes a torquelimiting device on the shaft ofsaid motor and a reducing gearing from said device to said drivemember.

6. A screw-jack device as in claim 1 wherein said tubular casingportion, said nut, said tube and said slidable seal between said tubeand said portion define a substantially air-tight enclosure forming apneumatic damping means for the emergency-projecting movement of saidassembly, and an adjustable vent aperture is provided for said enclosureto adjust the damping action thereof.

7. A screw-jack device comprising in combination a casing having anelongated tubular portion, a tube telescopable within said portion incoaxial spaced relationship therewith slidably sealed in the outer endof said portion, a structure to be operated by said device attached tothe outer end of said tube, a nut member at the inner end of said tubesealingly non-rotatably slidable in said tubular portion, and definingwith the inner end of said casing a sealed enclosure, a screw-rodengaging said nut and extending coaxially to said tubular portion andsaid tube, a reversible power-means outside said casing, a drive memberin said casing opposite the inner end of said rod and a drive connectionextending from said power-means to said drivemember, a cavity with acylindrical wall extending from said member towards said rod and acavity with a cylindrical wall extending from the inner end of said rodtowards said member surrounding said first caVity-Wall, clutch-teeth onthe end of said first cavity-wall and clutch-teeth in the end-wall ofsaid second cavity drivingly cooperating therewith when said rod isretracted within said casing for normal operation, annularly-spacedrecesses in the inner-cylindrical surface of said second cavity-wall andcomplementary apertures through said first cavity wall, a ball eachadapted when in a latching position, to be partly seated in each of saidrecesses and partly seated in a related one of said apertures, a pistonsealingly slidable in said first cavity defining a chamber with theend-wall thereof, a peripheral groove around said piston, spring meansurging said piston to a position wherein the periphery thereof retainssaid balls in said latching position thereof, a supply of pressure fluidoutside said casing, means to admit pressure fluid in an emergency fromsaid supply to said chamber to thereby urge said piston to an unlatchingposition wherein said groove allows said balls to be retracted from outof said respective recesses, a port through the cylindrical Wall of saidfirst cavity arranged to be uncovered by said piston only as said pistonis urged to said unlatching position to provide communication from saidchamber through said port to said enclosure, whereby said fiuid acts insaid enclosure first to force said balls to said retracted positionthereof and then to drive said nut, tube and screw assembly outwardly ofsaid casing.

8. In a screw-jack as claimed in claim 7, a push-rod extending from saidpiston axially and projecting from out of said casing to allow saidpiston to be manually actuated after said piston has operated in anemergency, both to uncover said port and thus allow the fluid in saidenclosure to be vented, and to allow retraction of said balls to thusenable said screw to return to the normal retracted position thereof.

-ROLAND LARAQUE.

REFERENCES CITED The following references file of this patent:

UNITED STATES PATENTS are of record in the

